1. Field of the Invention
The present invention is directed to medical devices of the type implantable in the body of a patient, and in particular to such devices having means for detecting physiological events and/or means for stimulating physiological events, and control logic to which the means for detecting and/or the means for stimulating are connected, and means for the telemetric transmission of data relating to the logic status of the control logic to an external receiver, the means for transmission of data being connected to the control logic.
2. Description of Prior Art
Devices of the type described above are known, for example, heart pacemaker or defibrillators, wherein the logic status of the control logic is dependent, among other things, on whether a physiological event was detected, or whether a physiological event was stimulated. When the physiological functions of the patient in which the events are detected and/or stimulated are represented as a function of time, i.e., as an electrocardiogram, and when the data relating to the logic status of the control logic are generated with those events in the correct chronological correspondence, it is possible to evaluate the interaction of the implanted device with the body of the patient. It is known to accomplish a readout of the logic status data non-evasively by the telemetric transmission of this data to an external receiver.
A device of this type is described in European published Application 0 120 250. This device is a heart pacemaker which stores data regarding a preceding heart or pacemaker cycle, and transmits the data to the receiver with a delay, namely when an event which terminates the cycle occurs. The data transmission thus ensues with a delay corresponding to the duration of a cycle. To represent the transmitted data in correct chronological allocation to an electrocardiogram of the patient, it is thus necessary to delay the representation of the electrocardiogram, which requires considerable outlay. Moreover, transmission of the data with respect to each cycle occurs only once. The risk of data loss is thus high. An effective correction of data transmission errors in the receiver is possible only to the extent that data which is obviously senseless can be suppressed.
Another device of this type is described in U.S. Pat. No. 4,374,382. In this known device, the detection of a physiological event or the stimulation of a physiological event causes the formation and transmission of a code corresponding to the event. The data transmission ensues quasi-simultaneously with the appearance of the event. Again, however, data transmission ensues only a single time per event. The risk of data loss is again high, and an effective error correction with respect to the transmitted data is not possible.